Recently portable and cordless tendency in electronic appliances for general use have been rapidly progressing. Accordingly, a demand for a small-sized, light-weight secondary battery having a high energy density, used for charge and discharge power supply for driving a motor, has been increasing. From this point of view, non-aqueous batteries, and particularly secondary lithium batteries are anticipated as batteries having high voltage and energy densities and the development of these batteries is urged. Conventionally, manganese dioxide, vanadium pentaoxide, titanium disulfide and the like have been used as a cathode active material of the secondary lithium batteries. Such a battery comprises a cathode of these materials, a lithium anode and an organic electrolyte and charge and discharge of electricity are repeated. However, in a secondary battery employing a lithium metal anode, the problems of internal short circuit caused by dendritic lithium generated upon charging or side reactions between an active material and an electrolyte are a barrier to developing useful secondary batteries. Further, there has not yet been found a secondary battery which satisfies the high rate charge and discharge property and the over discharge property.
The safety of the lithium batteries has been also severely pointed out and in battery systems employing a lithium metal or a lithium alloy therein as an anode, the safety is very difficult to ensure. On the other hand, a new type of negative electrode has attracted interest, in which the intercalating reaction of layered compounds is utilized for solving the above problems. Particularly graphite compound incorporating anions such as ClO.sub.4 -ion, PF.sub.6 -ion, BF.sub.4 -ion and the like is used as a cathode or positive electrode; and graphite compound incorporating cations such as Li+, Na+ and the like is supposed to be used as an anode or negative electrode.
However, intercalated graphite incorporating cations therein is very unstable, so that in the case of using natural or artificial graphite as an anode, the battery lacks stability and the capacity thereof is low. Further, since decomposition of the electrolyte takes place, intercalated graphite cannot be used in place of a lithium anode.
Lately, it has been found that lithium doped materials of pseudo graphite materials obtained by carbonization of a variety of hydrocarbon or polymeric materials are effective as an anode material and can exhibit a high efficiency and further have excellent stability in a battery. Accordingly, many researches on small-sized, light-weight batteries with the use of these materials have been made.
On the other hand, accompanied with use of carbon materials as an anode, it is proposed that such Li-contained compounds having higher voltage as LiCoO.sub.2 or LiMn.sub.20 O.sub.4 or composite oxide in which a part of Co and Mn is displaced by other elements such as, for example, Fe, Co, Ni, Mn and so on, are to be used as a cathode active material.
The amount of lithium occluded and released upon using the afore-mentioned pseudo graphite materials having more or less turbostratic structures as an anode material was measured to obtain the capacity of only 100-150 mAh/g carbon and also polarization of carbon electrode, accompanied with the electric charge and discharge, is intensified. Therefore, when these carbon anode materials are used in combination with a cathode of, for example, LiCoO.sub.2 and so on, it is difficult to obtain a satisfactory capacity and voltage.
On the other hand, it has been reported that in the case of using a high crystalline graphite material as an anode, intercalation reaction of lithium is difficult to proceed due to the gas generated upon charging on the surface of the graphite electrode surface by the decomposition of an electrolyte. It is found that in spite of generating the gases, coke and the like heat-treated at a high temperature gives relatively high capacity (200-250 mAh/g). However, due to the large expansion and contraction of the graphite in the C axis direction, accompanied with the charge and discharge, the anode body is swollen, by which the original shape cannot be kept. Therefore, there is a serious problem in the cycle property.
Thus, an object of the present invention is to provide a secondary battery with non-aqueous electrolyte, having high voltage, high capacity and an excellent cycle property, by which the above-mentioned conventional problems can be solved.